10 Key Points of Processing and Forming Modified Nylon PA6 Plus 30% Glass Fiber Reinforced Parts

30% glass fiber reinforced PA6 modification

30% glass fiber reinforced PA6 modified chip is an ideal material for processing electric tool casings, electric tool parts, construction machinery parts and auto parts. Its mechanical properties, dimensional stability, heat resistance, and aging resistance have been significantly improved, and its fatigue resistance is 2.5 times that of the unenhanced one. The modification effect is the most obvious.

The injection molding process of 30% glass fiber reinforced PA6 slices is roughly the same as that of unreinforced, but because the flow is worse than before the reinforcement, the injection pressure and injection speed should be appropriately increased. The processing points are as follows:

1. The temperature of 30% glass fiber reinforced PA6 barrel can easily increase by 10-40°C. The barrel temperature selected during injection molding of PA6 modified slices is related to the performance of the slice itself, equipment, and shape factors of the product. Excessively high material temperature will easily cause discoloration and brittleness of the workpiece, resulting in defects such as silver wires. Too low barrel temperature will easily harden the material and damage the mold and screw. The minimum melt temperature of PA6 is 220°C. Due to the good fluidity of nylon, it flows rapidly when the temperature exceeds its melting point. The fluidity of 30% glass fiber reinforced PA6 modified slices is significantly lower than that of pure material slices and injection-molded PA6 slices, and the barrel temperature is easy to increase by 10-20°C.

2. The mold temperature of 30% glass fiber reinforced PA6 is controlled at 80-120°C. Mold temperature has certain influence on crystallinity and molding shrinkage rate, and the range of mold temperature is 80-120℃. Products with high wall thickness should choose high mold temperature, which has high crystallinity, good wear resistance, increased hardness and elastic modulus, decreased water absorption, and increased molding shrinkage of the product. Thin-walled products should choose low mold temperature, which has low crystallinity, good toughness, high elongation and reduced shrinkage. If the wall thickness is greater than 3mm, it is recommended to use a low temperature mold at 20~40°C. 30% glass reinforced material mold temperature should be greater than 80 ℃.

3. The wall thickness of 30% glass fiber reinforced PA6 products should not be less than 0.8mm. The flow length ratio of PA6 is between 150-200, and the wall thickness of the product should not be less than 0.8mm, generally between 1-3.2mm. The shrinkage of 30% glass fiber reinforced PA6 products is related to its wall thickness, and the thicker the wall thickness, the greater the shrinkage rate.

4. The vent slot should be controlled below 0.025mm. The overflow value of 30% glass fiber reinforced PA6 resin is about 0.03mm, so the vent slot should be controlled below 0.025mm.

5. The gate aperture should not be smaller than 0.5*t (t is the thickness of the plastic part). With submerged gates, the minimum gate diameter should be 0.75mm.

6. The shrinkage rate of 30% glass fiber reinforced PA6 products can be reduced to 0.3%. The shrinkage rate of PA6 pure material is between 1% and 1.5%. After adding 30% glass fiber reinforcement, the shrinkage rate can be reduced to about 0.3%. Practical experience shows that the more glass fiber is added, the smaller the molding shrinkage of PA6 resin. However, as the amount of fiber added increases, it will also cause surface floating fibers and poor compatibility. The effect of 30% glass fiber reinforcement is relatively good.

7. The 30% glass fiber reinforced PA6 recycled material should not be used more than 3 times. 30% glass fiber reinforced PA6 does not contain any recycled material, but if the customer uses too much recycled material, it is easy to cause discoloration of the product or a sharp decline in mechanical and physical properties. The application amount should be controlled below 25%, otherwise it will cause fluctuations in process conditions. Recycled materials must be dried before being mixed with new materials.

8. The amount of release agent used is small and uniform. The release agent for 30% glass fiber reinforced PA6 products can be zinc stearate and white oil, etc., or it can be mixed into a paste for use. A small amount of release agent can improve and eliminate defects such as air bubbles. When used, the amount must be small and uniform, so as not to cause surface defects of the product.

9. After the product is out of the mold, put it in hot water to cool slowly. Since the glass fiber will be oriented along the flow direction during the injection molding process, the mechanical properties and shrinkage rate will be enhanced in the direction of orientation, resulting in deformation and warping of the product. Therefore, when designing the mold, the position and shape of the gate should be reasonable, and the temperature of the mold can be increased in the process. After the product is taken out, it should be placed in hot water to let it cool slowly.

10. The 30% glass fiber reinforced PA6 parts used in high temperature environment should be treated with humidity control. Boiling water can be used to adjust humidity, and potassium diacetate aqueous solution can also be used to adjust humidity. The boiling water humidity control method places the product in an environment with a humidity of 65% to achieve a balanced moisture absorption. Potassium acetate aqueous solution (the ratio of potassium acetate to water is 1.25:1, boiling point 121°C) the treatment temperature of the humidity control method is 80-100 °C potassium acetate aqueous solution humidity control method. The processing time mainly depends on the wall thickness of the product. When the wall thickness is 1.5mm, it takes about 2 hours; when it is 3mm, it takes about 8 hours; when it is 6mm, it takes about 16-18 hours

Adding glass fiber to PA6 is an effective strengthening method to improve the performance of engineering plastics. The products are widely used in electrical shells, air conditioner fan blades and five-star chair legs, etc., not only have high strength, but also have good matching accuracy. The following are additions to the processing essentials:

(1) Dry and dehumidify the material before processing, and use a dehumidification and heat preservation hopper throughout the injection process.

(2) In order to reduce wear and tear, the barrel and screw of the injection machine are coated with alloy metal to ensure high hardness.

(3) Choose an appropriate screw rotation speed to reduce wear and prolong life.

(4) Mold design, consider increasing the diameter of the runner and the cross-sectional size of the gate (commonly known as: large gate). To choose a slow high-pressure injection process, avoid jet injection, do not allow small gates and high-pressure, high-speed injection, which is conducive to reducing the internal stress of the part.

(5) There are other reasons besides the injection process for the fiber exposure. Because glass fiber and resin are mechanically mixed, the two are incompatible. If the quality of glass fiber degreasing is not good, the resulting parts will also have exposed fibers or delamination.

(6) For PA products, in order to ensure the quality and reduce the internal stress, after processing, humidity control treatment (water boiling method, etc.) is required, and it is cooled with water. Inspection method: soak and observe with polar solvent n-heptane. If the humidity is not adjusted or the treatment is not in place, the workpiece will crack.

(7) In order to obtain stable product quality, it is recommended to inlay high-hardness materials at the ingate of the mold, so that the size of the ingate can be continuously guaranteed.

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